SPECIFIED MATHEMATICAL MODEL OF THE DISSOLVED SUBSTANCES SMALL CONCENTRATIONS REFRACTOMETRICAL SENSOR INCLUDING SURFACE PLASMON EFFECT

Abstract

In a number of practical problems, there is a need to determine the concentration of substances whose mass (volume) fraction in the solution is quite small. Therefore, the task of determining the quantitative and qualitative composition of dissolved substances small concentrations  occupies an important place in various fields of science and technology.

The most common methods of dissolved substances small concentrations measuring, which are characterized by high speed and versatility, include refractometric methods. Among the mentioned methods, the method based on the use of the surface-plasmon resonance effect is of particular interest for solving the mentioned problem. Its main advantages include high sensitivity and the relatively small mass of the sample required for research. However, the wide use of this measurement method is significantly limited by the lack of high-precision mathematical models of primary measuring transducers (sensors) implemented on its basis.

The paper considered the main directions of the development of refractometry and its relevance in various spheres of human activity, such as science, technology, medicine and even the food industry. As a result of the need to use the phenomenon of the surface plasmon effect, a detailed description of this phenomenon, its features, essence and practical application is given. The peculiarity of the interaction of radiation with gold nanofilms is considered.

The mathematical model of the refractometer based on the surface plasmon effect was developed. A study of the model was carried out, as a result of which it was established that the stability of the radiation source power does not affect the measurement error. This makes it possible to develop simple and cheap measuring devices in which there is no need to stabilize the optical characteristics of the radiation source and the photoreceiver. The adequacy of the obtained conclusions was confirmed by computer modeling and experimental research.